IR cards are only used to "check/see the IR", since the effects of an SSY can easily be seen(punching holes through black paper); I'm not sure why you need one...
From Post Apple and use a CCD to watch the phosphor.. You can also see it through some safety glasses.
You can take a piece of mat ceramic tile, spray it with clear krylon, and dust it with the ZNS and see the hit for quite a few unfocused shots... A UV led or a mercury lamp pumps the phosphor..
Not all ZnS will do this, but I've had good luck with the cheaper stuff, however the long persistance stuff from United Nuclear doesn't work. Nor will most cr:yag or sr:yag phosphors from china via fleabay.. Also works quite well at 808 nm
You could try a finely crushed KTP crystal, but the crushing process causes stresses in the resulting powder and it doesn't always work well.
This can be carried out to Co2 wavelengths as well by a special material:
But its not cheap.. Remember a simple thick piece of AR coated glass can be used to pick off 1% of the beam and protect the cheaper viewing cards. But the pulse is so short you do not see much..
Thorlabs has something for 19$ a disk, but I suspect its a 1 shot wonder.
As Mike Says, I really hope you have a pair of ANSI certified wraparound YAG 0D6s made by a reputable company before working with a SSY1.
Leakage IR WILL find a way to your eyes if you don't.
With around 5mm beam diameter, 30mJ will softly tic on an IR card if it's already dark burnt, but the lighter areas don't get burned. What I used to make a beam profile is using a 45 deg HR mirror to divert the beam to a beamdump. The small leakage is falling on a camera with proper ND filters. The transmission was visible on a sensitive IR card with a few 100's of mJ, so you don't need much for that.